XTRABACKUP ERROR: InnoDB: Operating system error number 13 in a file operation.
 
SYMPTOM: When you receive an ‘access’ error similar to this…
 
   xtrabackup: Generating a list of tablespaces
  2017-02-20 08:28:32 7f875a611720  InnoDB: Operating system error number 13 in a file operation.
  InnoDB: The error means mysqld does not have the access rights to
  InnoDB: the directory.
  innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 2703
          main::wait_for_ibbackup_file_create(‘/dbdata/bkups_here/2017-02-20_08-28-32/xtrabackup_suspended_2’) called at /usr/bin/innobackupex line 2723
          main::wait_for_ibbackup_suspend(‘/dbdata/bkups_here/2017-02-20_08-28-32/xtrabackup_suspended_2’) called at /usr/bin/innobackupex line 1976
          main::backup() called at /usr/bin/innobackupex line 1601
  innobackupex: Error: The xtrabackup child process has died at /usr/bin/innobackupex line 2703. 
PROBLEM: XtraBackup is looking through the database list, even though a specific directory may have been specified, and having issues reviewing the databases containers. 
 
SUGGESTION: Review all ‘directories’ (databases) in the ‘datadir’ directory. Review the engine’s access (usually the ‘mysql’ user). RW access is required. In my case, even though ‘ignore-db-dir=lost+found’ was specified in the ‘my.cnf’, I had to remove the directory ‘lost+found’. 
Keywords: mariadb, mysql, percona xtrabackup, error